Thermal characteristics analysis and error prediction for lubricated multi-link high-speed precision presses

Enlai Zheng,Yuanzhao Yang,Zhaohui Peng,Yue Zhu,Xiao Zhao,Xiangze Lin,Min Kang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.6

Thermal models are important in the process of predicting the thermal characteristics and corresponding thermal error of multi-link high-speed precision presses (MLHSPPs) with an oil-lubrication system. Previous models only involved the effects of bearing stiffness, temperature change of bearings, flexibility of crank shaft on the heat generation power, while the influences of revolute clearance joint and flexibility of linkage are seldom considered, which inevitably reduces the accuracy of thermal analysis. To overcome this problem, dynamic models of flexible multi-link mechanisms (MLM) with clearance, lubrication, crankshaft-bearing system are constructed, the interaction forces between pin and bushing are obtained to calculate its heat generation power. Then, an improved model of MLHSPP with lubrication is proposed to analyze the temperature evolution and the thermal error between slider and work table at the position of LDP, by considering bearing stiffness, temperature change of bearings, flexibility of crank shaft, linkage, clearance, lubrication and thermal contact resistance all together. Compared with results from traditional models, the simulation data from this improved thermal model agree well with experiment, which proves the validity of the proposed model. Furthermore, the temperature rise and the thermal error of MLHSPP between slider and work table at the position of LDP under different input speeds, lubricating oil flux and contact angles of ball bearing were also studied.

Microarrays for the Detection of HBV and HDV

Sun, Zhaohui,Zheng, Wenling,Zhang, Bao,Shi, Rong,Ma, Wenli Korean Society for Biochemistry and Molecular Biol 2004 Journal of biochemistry and molecular biology Vol.37 No.5

The increasing pace of development in molecular biology during the last decade has had a direct effect on mass testing and diagnostic applications, including blood screening. We report the model Microarray that has been developed for Hepatitis B virus (HBV) and Hepatitis D virus (HDV) detection. The specific primer pairs of PCR were designed using the Primer Premier 5.00 program according to the conserved regions of HBV and HDV. PCR fragments were purified and cloned into pMD18-T vectors. The recombinant plasmids were extracted from positive clones and the target gene fragments were sequenced. The DNA microarray was prepared by robotically spotting PCR products onto the surface of glass slides. Sequences were aligned, and the results obtained showed that the products of PCR amplification were the required specific gene fragments of HBV, and HDV. Samples were labeled by Restriction Display PCR (RD-PCR). Gene chip hybridizing signals showed that the specificity and sensitivity required for HBV and HDV detection were satisfied. Using PCR amplified products to construct gene chips for the simultaneous clinical diagnosis of HBV and HDV resulted in a quick, simple, and effective method. We conclude that the DNA microarray assay system might be useful as a diagnostic technique in the clinical laboratory. Further applications of RD-PCR for the sample labeling could speed up microarray multi-virus detection.

Joint Deployment and Task Computation of UAVs in UAV-assisted Edge Computing Network

Yuqing Chen,Zhaohui Zheng 한국통신학회 2020 한국통신학회 APNOMS Vol.2020 No.09

Unmanned Ariel Vehicle(UAV) has been widely used in the edge computing network. Owing to its line-of-sight communication ability and mobility, it has offered task offloading service and some task computation for mobile devices(MDs). Nowadays, as high-intensity calculation application develops rapidly, maximizing the size of offloaded tasks is necessary for meeting the users’ experience in applications. In this context, our paper takes research on how to deploy UAVs at the most proper place to offer task offloading with TDMA protocol. Specifically, we will optimize the task offloading number in the MDs-UAV system by combining the location of UAVs, the task computation capacity of UAV, and the MDs-UAV associations in a certain time. We prove that the joint UAV deployment and task computation problem is NP-hard, and use a greedy algorithm to optimize the result. Compared with randomly selected method, our simulation shows that the greedy algorithm performs greatly and the deployment of UAVs are sensible. We believe that this idea will improve the system tasks processing rate and Quality of Experience(QoE) of mobile users.

Experiment research on grind-hardening of AISI5140 steel based on thermal compensation

Xiangming Huang,Yinghui Ren,Bo Zheng,Zhaohui Deng 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.8

The grind-hardening process utilizes the heat generated to induce martensitic phase transformation. However, the maximum achievable harden layer depth is limited due to high grinding forces, and the tensile residual stress appears on the ground surface in the grindhardening process. This paper proposes a new grind-hardening technology using thermal compensation. The workpiece of AISI5140 steel is preheated by electric resistance heating, and ground under the condition of the workpiece temperature 25°C, 120°C, 180°C and 240°C. The grinding force, harden layer depth and surface quality including residual stress on ground surface, surface roughness and micro-hardness are investigated. The experimental results show that a deep harden layer with a fine grain martensite can be obtained with the thermal compensation. The ground workpiece surface produces a certain compressive residual stress, and the residual compressive stress value increases with preheating temperature. As the preheating temperature increases, grinding force slightly decreases, while there is slightly increment of surface roughness. Compared with the conventional grind-hardening process, both the harden layer depth and residual stress distribution are significantly improved.

A BIO-INSPIRED POLYDOPAMINE APPROACH TO PREPARATION OF GOLD-COATED Fe3O4 CORE-SHELL NANOPARTICLES: SYNTHESIS, CHARACTERIZATION AND MECHANISM

PENG AN,FANG ZUO,XINHUA LI,YUANPENG WU,JUNHUA ZHANG,ZHAOHUI ZHENG,XIAOBIN DING,YUXING PENG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2013 NANO Vol.8 No.6

A biomimetic and facile approach for integrating Fe3O4 and Au with polydopamine (PDA) was proposed to construct gold-coated Fe3O4 nanoparticles (Fe3O4@Au–PDA) with a core–shell structure by coupling in situ reduction with a seed-mediated method in aqueous solution at room temperature. The morphology, structure and composition of the core–shell structured Fe3O4@Au–PDA nanoparticles were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectrometry (XPS). The formation process of Au shell was assessed using a UV-Vis spectrophotometer. More importantly, according to investigating changes in PDA molecules by Fourier transform infrared spectroscopy (FTIR) and in preparation process of the zeta-potential data of nanoparticles, the mechanism of core–shell structure formation was proposed. Firstly, PDA-coated Fe3O4 are obtained using dopamine (DA) self-polymerization to form thin and surface-adherent PDA films onto the surface of a Fe3O4 "core". Then, Au seeds are attached on the surface of PDA-coated Fe3O4 via electrostatic interaction in order to serve as nucleation centers catalyzing the reduction of Au3+ to Au0 by the catechol groups in PDA. Accompanied by the deposition of Au, PDA films transfer from the surface of Fe3O4 to that of Au as stabilizing agent. In order to confirm the reasonableness of this mechanism, two verification experiments were conducted. The presence of PDA on the surface of Fe3O4@Au–PDA nanoparticles was confirmed by the finding that glycine or ethylenediamine could be grafted onto Fe3O4@Au–PDA nanoparticles through Schiff base reaction. In addition, Fe3O4@Au–DA nanoparticles, in which DA was substituted for PDA, were prepared using the same method as that for Fe3O4@Au–PDA nanoparticles and characterized by UV-Vis, TEM and FTIR. The results validated that DA possesses multiple functions of attaching Au seeds as well as acting as both reductant and stabilizing agent, the same functions as those of PDA.

Preparation and Self-Healing Behaviors of Poly(acrylic acid)/Cerium Ions Double Network Hydrogels

Hongwei Zhou,Guohe Xu,Jie Li,Shihao Zeng,Xiaolong Zhang,Zhaohui Zheng,Xiaobin Ding,Weixing Chen,Qiguan Wang,Wenzhi Zhang 한국고분자학회 2015 Macromolecular Research Vol.23 No.12

This work aims at developing an approach to poly(acrylic acid)/cerium ions (PAA/cerium ions) double network hydrogels and exploring the self-healing properties of the hydrogels, with expectation to provide some clues for constructing new healable gel actuators and enrich the family of self-healable hydrogels. The hydrogel is covalently crosslinked by a traditional crosslinking agent N,N'-methylene bis-acrylamide to form the first network and further physically crosslinked by the ionic interaction between cerium ions and the carboxyl groups in the hydrogel network. The preparation method and self-healing behaviors of the hydrogels are investigated.